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  • #16
    Originally posted by MattiJ View Post
    I dont like CCGT for boring bars that much, very small clearance between the bar and bore resulting in chips wedging between. DCGT or TCGT works better if bore size allows.
    This sounds very much like the problem I was having. Any preference between the two? TCGT presumably has the benefit of three cutting points but if that's at the expense of exactly what I'm trying to get more of, it's a poor trade. DCGT is smaller (due to angles) which could be a good thing if it doesn't make it more fragile?

    Originally posted by MattiJ View Post
    60mm depth with 12mm bar is also pushing your luck. Its doable but you are fighting with chatter at some point for sure.
    It definitely was on the tiny bar....but I knew that. I didn't notice problems with the 12mm bar that I could attribute to flex. It was definitely more what you might call "crunchy" towards the blind end, but I'm pretty sure that was chip recutting.

    deltap I was thinking the same as a workaround. I feel there may be a set of 2MT drills in the near future

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    • #17
      So I read you have a mini lathe, running 1700, doing ID boring, in a 24mm bore, in some kind of an aluminum.
      Some wisdom mentioned before, the final pass is what counts to bring it to final size.
      This .5mm (.020") depth of cut is a lot for such a whimpy lathe.
      No wonder you have trouble.
      Take smaller cuts, slow it the heck down, get some positive geometry with a chip breaker to curl the chip,
      and take some spring final passes. I don't see predictive stock removal happening here.

      -Doozer
      DZER

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      • #18
        Originally posted by Doozer View Post
        So I read you have a mini lathe, running 1700, doing ID boring, in a 24mm bore, in some kind of an aluminum.
        Some wisdom mentioned before, the final pass is what counts to bring it to final size.
        This .5mm (.020") depth of cut is a lot for such a whimpy lathe.
        No wonder you have trouble.
        Take smaller cuts, slow it the heck down, get some positive geometry with a chip breaker to curl the chip,
        and take some spring final passes. I don't see predictive stock removal happening here.

        -Doozer
        I don't know about 20 thou being a lot for a small lathe. I've got a 100 year old 8" lathe, plain bearings, and it will happily do 50 thou DOC in cast iron at 200rpm, using a tipped tool. Good finish too.
        'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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        • #19
          Originally posted by Richard P Wilson View Post

          I don't know about 20 thou being a lot for a small lathe. I've got a 100 year old 8" lathe, plain bearings, and it will happily do 50 thou DOC in cast iron at 200rpm, using a tipped tool. Good finish too.
          I don't think a mini-lathe has a back gear, but maybe I am wrong.

          -D
          DZER

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          • #20
            Originally posted by Doozer View Post

            I don't think a mini-lathe has a back gear, but maybe I am wrong.

            -D
            You're not. No back gears at all but it is at least a brush less DC motor so it doesn't lose all torque at the low end. Also no gearbox and the carriage dial graduations don't match up with actual travel. Ya pays yer money and all that. Still, with my space constraints it wasn't a bad fit - old iron might have been better (minefield if you've no clue what you're doing though) but probably twice the size or more.
            For the purposes of fair comparison, this probably shouldn't be called a mini lathe. Not saying that it's a proper "big boy" lathe but it's one (maybe even two) up in size from what they're selling as "mini".

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            • #21
              Originally posted by Doozer View Post

              I don't think a mini-lathe has a back gear, but maybe I am wrong.

              -D
              No, apparently its a Sieg SC4, with a variable speed DC motor, lowest spindle speed 150rpm, so it won't have much 'grunt' left at that speed, unlike my old beastie which has maximum torque at its lowest speed of 25rpm.
              'It may not always be the best policy to do what is best technically, but those responsible for policy can never form a right judgement without knowledge of what is right technically' - 'Dutch' Kindelberger

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              • #22
                I think you're probably just hitting the limitations of your machine unfortunately. I did a lot of work on an Atlas 618 (similar size/ weight as your SC4) and even in alu I had birds nesting and needed to do several spring passes boring alu with a CCGT insert. Still made good parts, just took longer than I would have liked. Fast forward to my South Bend wide 9 and I tried out a TCGT boring bar. I think I was taking 50 thou or more per pass, 8 or 900rpm and chips were spraying everywhere. It was amazing. Doesn't help you much I know, but you may have to just get used to what you have until you can get something beefier.

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                • #23
                  An old trick is to turn the boring bar up- side down and turn on the far side. Now your dials read the same as turning the OD. Sometimes you get less chatter too. You wont strain your neck trying to look down the bore.

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